1. Field
The present invention relates to an enclosure structure of an electronic apparatus and to an electronic apparatus, and particularly to an enclosure structure of an electronic apparatus having ribs for reinforcing the enclosure and to an electronic apparatus.
2. Description of the Related Art
In an enclosure (exterior casing, housing, etc.) of an electronic apparatus such as a personal computer, etc., a substantially box-shaped concave portion for storing various functional parts, such as a battery pack, hard disk drive (HDD), extension memory, modem, wireless LAN module, key array (keyboard), etc., is integrally molded. Further, the concave portion is composed of a bottom wall and a surrounding wall. Furthermore, an outer wall is formed so as to enclose the concave portion and, in addition, a connecting wall for connecting the upper end portion of the outer wall and the upper end portion of the concave portion is integrally molded.
As a material for constituting the enclosure, generally a thermoplastic resin such as acrylic resin (ABS resin), etc., has been widely used. Furthermore, an injection molding method and a compression molding method are generally used for molding the enclosure from a viewpoint of being able to mold a lot of products (molded articles) each having a complicated shape quickly and to adopt automatic controlling system.
Furthermore, when the enclosure made up of the concave portion, the outer wall, and the connecting wall is constructed by using one thin continuous mold body, since the rigidity is decreased in the curved portion of a large curvature and the connecting wall of a large area of the enclosure, deformation is easily caused by surface shrinkage immediately after the molding process, and there is posed a problem in that the accuracy of the shape of molded products is lowered and the product yield is reduced due to visual defects.
Then, in order to solve the aforementioned problem of the decreasing rigidity of the enclosure, there has been also conventionally adopted an enclosure structure in which reinforcement ribs for connecting the external surface of the surrounding wall of a concave portion for storing the functional parts and the inner surface of the outer wall of the enclosure are formed.
Furthermore, as a conventional enclosure structure, there has been proposed a portable computer enclosure structure in which a thick-wall portion where the thickness of a wall portion of an enclosure is partially increased at a reinforcing position is formed, a pinhole is provided inside the thick-wall portion, a reinforcement rib is formed such that the thick-wall portion is expanded by injecting a gas into the pinhole, the width of the reinforcement rib is made larger than the wall thickness of the enclosure, and the rigidity is increased (for example, Japanese Registered Utility Model No. 3056719).
However, in the conventional molded enclosure structure of an electronic apparatus in which thick-wall portions are partially formed at reinforcing positions of an enclosure, pinholes are provided in those thick-wall portions, and reinforcement ribs are formed such that the thick-wall portions are expanded by injecting a gas into the pinholes, a high degree of technology is required to form the pinholes, it is difficult to form a thick-wall portion of a constant thickness, and there is a problem in that variations (scatterings) in the rigidity and strength of the enclosure increase.
On the other hand, in the conventional molded enclosure structure of an electronic apparatus in which the reinforcement ribs for connecting the outer surface of the surrounding wall of the concave portion and the inner surface of the outer wall of the enclosure are formed, there is a problem in that warpage and deformation of the enclosure caused by shrinkage at the time of molding and dimensional variations of the enclosure caused by surface shrinkage increase, and the production yield is disadvantageously reduced due to the inferior appearance of the products. In particular, in the enclosure in which a substantially box-shaped concave portion for storing the functional parts is integrally formed, since the substantially box-shaped concave portion has a relatively high rigidity at a time immediately after the molding, the outer surrounding portion of the enclosure is pulled in the direction of the concave portion through the reinforcement ribs due to shrinkage of the mold. As a result, the quality of the exterior appearance of the outer surrounding portion is likely to be degraded and deteriorated. That is, shrinkage is caused at the positions where the outer wall of the enclosure and the reinforcement ribs are connected, and there is posed a problem in that shrink marks, that is, surface irregularities are partially caused, thus resulting in visual defects.